Null references redux

[Christopher Wright]

Andrei Alexandrescu wrote:
> Walter Bright wrote:
>> Justin Johansson wrote:
>>> Walter, in the heat of this thread I hope you haven't missed the 
>>> correlation with discussion
>>> on "Dispatching on a variant" and noting:
>>
>> Thanks for pointing it out. The facilities in D enable one to 
>> construct a non-nullable type, and they are appropriate for many designs. 
> 
> No. There is no means to disable default construction.

I looked into this slightly. You'd have to do mark non-nullable fields 
as requiring ctor initialization, prevent reallocating arrays of 
non-nullables, and a few other things. At the time I wasn't considering 
struct constructors; without them, you'd have to forbid structs that 
contain non-nullable fields, but with them, it's okay.

>> I just don't see them as a replacement for *all* reference types.
> 
> Non-nullable references should be the default.
> 
> 
> Andrei